The present invention relates to a method for A/D conversion of analog signals using A/D converters, and to an appropriate A/D converter configuration.
In complex applications, different analog input signals need to be supplied to an A/D converter and converted in response to various events. The input signals to be converted can be requested at will by different request sources. In this context, the request sources produce request signals for the conversion selection method in order thus to request the A/D conversion of a particular signal channel in the A/D converter.
The constantly increasing number of input channels in A/D converter configurations and the fact that A/D conversion generally involves very time-critical applications make precise observance of the sequence of the signals to be converted absolutely necessary. This is particularly relevant if the analog signals supplied originate not just from an individual request source, such as a timer or a software application, but from a multiplicity of different request sources. In this case in particular, with requests for A/D conversion being supplied to the A/D converter configuration simultaneously, these requests need to be processed according to prescribed decision criteria (order) and, in particular, on the basis of their importance.
It is accordingly an object of the invention to provide a method for A/D conversion of analog signals, and an A/D converter configuration which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, in which a definable order of processing is provided and which allows A/D conversion for simultaneously present requests for A/D conversion. In particular, the aim of the invention is to allow preferential processing of important A/D converter requests.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for analog-to-digital (A/D) conversion of signals. The method includes the steps of:
a) transmitting a request signal for requesting A/D conversion of an analog signal from at least one of a plurality of converter request sources and each of the converter request sources has an assigned priority;
b) selecting a converter request source requesting the A/D conversion having a highest priority assigned to it; and
c) submitting the analog signal requested by the converter request source to an A/D converter for performing the A/D conversion.
According to the present invention, the A/D converter is provided for processing or converting analog signals which are each requested by different A/D converter request sources. Each A/D converter request source, in response to definable results, produces a request for one or more arbitrary signal channels in order to prompt A/D conversion of the appropriate signal by the A/D converter. In this context, the case may arise that requests from different A/D converter request sources are made simultaneously. To be able to overcome this problem, the present invention provides for each request source to have a settable priority assigned to it. As soon as there are requests from request sources for A/D conversion, that request source requesting A/D conversion which has the highest priority assigned to it at this instant is selected, and the requested analog signal from the selected request source is supplied to the A/D converter.
The prioritization or arbitration method (i.e. selection method) proposed according to the present invention can be used to create complex priority structures and to administer them without any additional software or CPU complexity. In particular, a multiplicity of requests from different request sources can be processed in accordance with the application, and hence in accordance with priority. Advantageously, the priorities may be assigned to the different request sources at will and may be freely programmed, so that the A/D converter configuration proposed according to the present invention may easily be matched to the respective requirements. The decision regarding the order in which the individual signal channels are to be converted is automatically made by the hardware of the A/D converter configuration, without any software intervention.
Since, as a rule, each A/D converter request source can request a plurality of channels with appropriate analog signals, it is advantageous that, after the A/D converter request source to be processed has been selected (source prioritization), selection of that signal channel of the previously selected A/D converter request source which is actually to be processed may additionally be provided (channel prioritization) in order thus to determine a particular channel for the A/D conversion when there are request pulses for a plurality of channels of the A/D converter request source already selected previously. The channel to be processed can likewise be selected using a definable priority rule.
In accordance with an added feature of the invention, there is the step of assigning each of the converter request sources a different priority.
In accordance with an additional feature of the invention, there is the step of continually checking each of the converter request sources to determine if a request for A/D conversion is being made by any of the converter request sources. And, if a request from a requesting converter request source has been detected, determining if the requesting converter request source has a higher priority assigned to it than another one of the converter request sources from which the request for A/D conversion has likewise been detected.
In accordance with another feature of the invention, there is the step of selecting the converter request source which has been received first in time, if request signals are simultaneously provided by different ones of the converter request sources having equivalent priorities in each case.
In accordance with further feature of the invention, the priorities assigned to the converter request sources are freely programmable and can thus be changed at will.
In accordance with another added feature of the invention, each of the converter request sources can request analog signals from a plurality of signal channels. And after a respective converter request source has been selected resulting in a selected converter request source, a corresponding signal channel corresponding to the request of the selected converter request source is selected, and the analog signal corresponding to the corresponding signal channel is converted by the A/D converter.
In accordance with another additional feature of the invention, there is the step of selecting the corresponding signal channel of the selected converter request source on a basis of a predetermined priority algorithm, and a corresponding analog signal for the corresponding signal channel selected is supplied to the A/D converter.
In accordance with another further feature of the invention, the converter request source requests A/D conversion by the A/D converter if the request signal for A/D conversion is present for at least one signal channel of the signal channels associated with the converter request source.
With the foregoing and other objects in view there is further provided, in accordance with the invention, an analog-to-digital (A/D) converter circuit containing an A/D converter for A/D conversion of analog signals. A multiplicity of analog signal channels is provided through which an appropriate number of the analog signals can be supplied to the A/D converter. A multiplicity of converter request sources for requesting at least one of the analog signal channels is further provided. The converter request sources generates request signals for requesting A/D conversion of an analog signal associated with a respective signal channel at arbitrary instants. Each of the converter request sources has a priority assigned to it. Selection devices are provided that are each connected to one of the converter request sources and the A/D converter. The selection devices select from the converter request sources requesting the A/D conversion, those of the converter request sources which presently have a highest priority assigned to them, and the selection devices supply the analog signal requested by a selected converter request source to the A/D converter for A/D conversion.
In accordance with an added feature of the invention, the selection devices are configured such that they successively carry out a check of each of the converter request sources to determine if any of the converter request sources is generating a request signal for A/D conversion by the A/D converter. If the request signal from a respective converter request source has been detected, the selection devices determine if the respective converter request source has a higher priority assigned to it than another converter request source from which the request signal for the A/D conversion has likewise been detected.
In accordance with an additional feature of the invention, the selection devices are configured such that, if the request signals are simultaneously provided by different ones of the converter request sources having equal priorities in each case, the selection devices select a respective converter request source which has been checked first in time.
In accordance with another feature of the invention, at least one of the selection devices has a storage device for storing the priority assigned to each of the converter request sources. The storage device and the priority of each of the converter request sources are freely programmable.
In accordance with a further feature of the invention, at least one of the converter request sources contains a control register in which a marker corresponding to a request signal is set when the A/D conversion is requested. The selection devices check for the presence of the request signal from the converter request sources by checking a content of the control register. Each of the converter request sources can request the analog signals from the multiplicity of analog signal channels, and each of the converter request sources sets the marker in the control register if there is a request for A/D conversion present for at least one of the analog signal channels.
At least one of the converter request sources contains a further control register, and each of the analog signal channels associated with a respective converter request source is allocated a specific bit array stored in the further control register. A marker is set in the specific bit array of the further control register if there is a request present for A/D conversion of one of the analog signal channels. The converter request sources are configured such that they set the marker in the control register if the marker indicating the request for the analog signal channel is set in the specific bit array of the further control register.
A further selection device is connected between the A/D converter and one of the selection devices and also between the selection devices. The further selection device is configured such that, after one of the converter request sources requesting A/D conversion has been selected, the further selection device selects a particular one of the analog signal channels and supplies the analog signal corresponding to the particular one of the analog signal channels to the A/D converter.
The further selection device is also configured such that, if simultaneous requests are present for A/D conversion of a multiplicity of the analog signal channels related to a selected converter request source, the further selection device selects the analog signal channel which corresponds to a highest-value bit array which is contained in the further control register of the selected converter request source that has the marker set.
In accordance with a concomitant feature of the invention, after a start of the A/D conversion, the marker in the further control register of the selected converter request source that corresponds to the selected signal channel is erased.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for A/D conversion of analog signals, and an A/D converter configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.